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Testing a method to evaluate the effectiveness of water enhancing gel on

vertical surfaces

Peter de Bruijn

Introduction

Test-burns conducted by FPInnovations in 2005 demonstrated that the application of water enhancing gel is a

viable method for structure protection under wildland fire conditions (Walkinshaw and Ault 2008; Walkinshaw

and Ault 2009). FPInnovations continues to expand its knowledge of firefighting gels in order to provide useful

information to the wildfire community.

In June 2010, three companies that distribute water enhancing gel products in Canada were invited to

participate in burn trials to test a method of assessing the effectiveness of water enhancing gels on vertical

surfaces. This project was planned in conjunction with other work to be conducted at the Canadian Boreal

Community (CBC) FireSmart Project site near Fort Providence, NT, Canada.

Fire protection ratings for building materials and certifications of water enhancing gel products are based on

extensive testing under laboratory conditions. Testing these materials and equipment under actual wildfire

conditions can be difficult to achieve and the CBC site provides a unique opportunity for testing under crown

fire situations.

The main objective of this project was to test a potential method for evaluating gel effectiveness on vertical

surfaces under wildfire conditions. Researchers wanted to determine whether cubes constructed with T1-11

plywood siding could be successfully used for gel application and then subjected to a high intensity crown fire.

A secondary objective was to obtain a basic understanding of how long water-enhancing gels, applied to

vertical surfaces, would remain effective as a barrier to fire ignition.

Methods

Nine 4-foot cubes were constructed using all-wood T1-11 plywood siding (Figure 1). T1-11 siding is used by the

WFCS1 in their standard test procedures for the evaluation of wildland fire chemicals. The cubes were placed in

the burn site in 3 groups of 3. Each company was provided one cube in each group. Each cube group had

different application times.

1 Wildland Fire Chemical Systems, Missoula Technology and Development Centre. Missoula MT.

Evaluation of Wildland Fire Chemicals STP 2.2 [http://www.fs.fed.us/rm/fire/wfcs/tests/stp02_2.htm]

Final Report September 2010

Wildfire Operations Research

1176 Switzer Drive

Hinton, AB T7V 1V3

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Figure 1. T1-11 plywood siding (R) and cubes in Group 2 at the burn site (L).

Representatives from the three gel companies each applied their own product according to their listed

recommended specifications. All products were applied using the same pumping system to provide consistent

water pressure and flow. Although the gel company representatives each provided their own nozzles, all used a

similar Akron Brass 1” Self-Educting Gel Forestry Nozzle #1230. Gel was applied to all four vertical surfaces and

the horizontal (top) surface.

Figure 2. Akron Brass 1” self-educting forestry nozzle.

FPInnovations researchers recorded the following:

• start time and duration (minutes and seconds) of application

• water volume used per application

• volume of gel concentrate used per application

• gel thickness and physical appearance on the vertical surfaces immediately after application, then 1

and 2 hours following application (Figure 3)

• post-fire condition of the cubes and gel product

In-fire video cameras were used to document the passage of the fire front and the effect of the fire on the gel-

treated cubes. Temperature data loggers recorded the time of fire encroachment and in-fire temperatures.

On-site weather data (temperature, RH%, wind speed) were obtained using an FTS weather station and hand

held Kestrel weather instrument.

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Figure 3. Recording of gel thickness and appearance.

Results

The test was conducted June 24, 2010. Gel was applied to each cube group in 1-hour intervals; gel application

times for each group were approximately:

Group 1 12:00 HRS

Group 2 13:00 HRS

Group 3 14:00 HRS

The thickness of the applied gels varied considerably and ranged from 2.0 to 4.5 mm (Table 2); average

thickness was relatively consistent for each product. Gel appearance varied between the three different

products, ranging from a smooth, tight film to an almost coarse stucco-like consistency.

Ignition time was 16:00 HRS. Weather conditions during the burn period (16:00 - 17:00) were:

• temperature 28.7°C

• relative Humidity 29%

• wind Speed (avg) 9.5 km/h

• wind Speed (max) 25.8 km/h

Crown fire developed quickly and the fire encroached on the cubes at approximately 16:10 HRS. The average

rate-of-spread in the area of the cubes was 14.8 m/min. Maximum temperatures recorded throughout the

burn plot ranged from 662 to 1023°C; the average maximum temperature during passage of the flame front

was 802°C. The average time span during which temperatures exceeded 100°C in the vicinity of the cubes was

4 min 36 sec (Table 2). The in-fire video showed an intense flame front as it approached the cubes. Fire

intensity (flame length and flame front) appeared consistent within the vicinity of the cube groups.

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Table 2. Gel application details.

Cube

Group

Application

Time

Gel Mix

Ratio

(%)

Gel

Thickness

(mm)

Time between

application and

fire passage

1 12:00 4.9 3.0 4 h, 10 min

1 12:17 6.2 2.0 3 h, 53 min

1 12:28 4.8 4.5 3 h, 42 min

2 12:51 5.6 4.6 3 h, 19 min

2 13:02 6.5 3.1 3 h, 08 min

2 13:16 8.5 2.0 2 h, 54 min

3 13:51 7.8 NO DATA 2 h, 19 min

3 13:55 10.3 NO DATA 2 h, 15 min

3 14:03 13.5 NO DATA 2 h, 07 min

All three groups of cubes survived the fire (Figure 4). Minimal charring was observed on 20 of the 36 vertical

surfaces (4 per cube, 12 per group). The degree of charring2 ranged from 1- 5% and char was primarily on those

surfaces that faced the fire front (east facing) and those that received the most solar radiation (south facing).

Figure 4. Group 1 after the fire.

2 An ocular estimate.

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Discussion

The primary objective of this trial was to test a potential method of evaluating gel performance on vertical

conditions under wildfire conditions. Secondary, was to gain a basic understanding of gel effectiveness on

vertical surfaces and determine whether application time is a critical factor.

All three groups of cubes survived the passage of an intense crown fire with only minimal charring of the T1-11

plywood siding. The observed differences in gel thickness and consistency between the three different

products did not appear to influence the effectiveness of the gels in preventing ignition of the cubes. As well,

the application time did not appear to have an effect on gel performance.

Compaction of the forest floor by field crews and researchers, and over-spray of gel onto the forest floor fuels

likely reduced the fire intensity in the immediate vicinity of each cube. However, both these conditions are

likely to occur during structure protection operations in an actual wildfire event.

When researchers compared the actual volume of gel-concentrate used in each application to what should

have been used based on water volume and nozzle settings, they found that in all cases actual gel concentrate

volumes used were far greater than what was expected. This resulted in gel mix-ratios of 4.8-13.5%; far in

excess of the manufacturers’ recommended mix-ratios (1-3%) and the specifications listed on the USDA Forest

Service Qualified Products List for water enhancers. On June 25, representatives from the three gel companies

tested the pump and spray systems (Figure 5). They found that the flow rates generated by the pump ranged

between 10.85-11.89 USG/min and the pressure at the nozzle was 90 psi. Tests also showed that the nozzles

educted the gel concentrate in amounts well above that which would result in the maximum recommended

mix ratio of 3%, regardless of the dial setting. Information received after the test revealed that optimum

performance of the Akron nozzle requires a minimum pressure of 100 psi and a minimum flow rate of 15

USG/min. In addition, the rate at which the gel concentrate is educted can be affected by the viscosity and

temperature of the concentrate. The flow rates produced in this study were clearly lower than optimal.

Figure 4. Flow and pressure evaluations on June 25.

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Although the excellent gel performance results may have been partly attributed to the higher than

recommended mix-ratios, the gels nevertheless prevented ignition of combustible surfaces under crown fire

conditions for up to four hours after application.

During the early evening hours on June 25, a considerable rain event produced 48 mm of precipitation at the

test site, which was sufficient to prevent further burn operations for the 2010 test season.

Conclusion

This exploratory work suggests that cubes constructed with T1-11 plywood siding, applied with gel and

subjected to a wildfire is a suitable means of field testing water-enhancing gels on vertical surfaces. This

approach may also help provincial fire management agencies further their understanding of the capabilities

and limitations of water enhancing gels. These trials also demonstrated the viability of water enhancing gels in

preventing ignition of wood surfaces under wildfire conditions.

Although this test produced some good results, some modifications in the test procedure would improve

results and subsequent analyses. Researchers and representatives from the gel companies felt the following

should be considered for future tests:

• add an un-treated cube to each cube group, as a test control

• measure overspray on the ground fuels surrounding the cubes

• record observations of the post-fire condition of the ground fuels surrounding the cubes

• clearly mark cube surfaces to be visible in photos and video

• record changes in the appearance or thickness of the gel in the hours prior to fire ignition

• record heat flux, a critical factor in the ignition of wood surfaces

• record the effort (time and equipment) required to clean gel from the cubes after the test

• use a pump with flow and pressure ratings that meet the nozzle manufacturer’s specifications for

optimum performance

• use a flow meter and pressure gauge to accurately measure water flow and pressure

• develop a method to accurately measure gel concentrate used

• measure the temperature of the water and the gel concentrate

• measure gel viscosity with a Brooksfield viscometer or Marsh Funnel

Acknowledgements

We gratefully acknowledge the support of ICL Performance Products LP, Thermo-Gel and Wildfire

Environmental Inc. We also thank the community of Fort Providence and the Government of the Northwest

Territories for their continued support and assistance in testing new products and technologies.

PARTNERS:

• Government of the Northwest Territories

• FPInnovations

• ICL Performance Products LP

• Thermo-Gel

• Wildfire Environmental Inc.

• Alberta Sustainable Resource Development

• Montane Forest Management

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References

Walkinshaw, S., Ault, R. 2008. Use of sprinklers and aqueous gel for structure protection from wildfire.

FPInnovations Advantage Report. Vol. 9. No. 8. 2008.

Walkinshaw, S., Ault, R. 2009. Use of sprinklers and aquesous gel for structure protection from wildfire – case

study 2. FPInnovations Advantage Report. Vol. 11. No. 3. 2009.